The present disclosure relates to a multilayer ceramic electronic part to be embedded in a board and a printed circuit board having a multilayer ceramic electronic part embedded therein.
As an electronic circuit has undergone high densification and high integration, mounting areas of a printed circuit board on which passive elements can be mounted have decreased, such that an effort to achieve an embedded device, a part embedded in a board, has been conducted. In particular, various methods in which a multilayer ceramic electronic part used as a capacitive part is embedded within the substrate have been suggested.
As a method of embedding the multilayer ceramic electronic part in the board, a board material itself may be used as a dielectric material for the multilayer ceramic electronic part and a copper wiring, and the like, may be used as an electrode for the multilayer ceramic electronic part. Alternatively, a polymer sheet having a high dielectric constant or a thin film dielectric may be formed in the board to manufacture the multilayer ceramic electronic part to be embedded in the board, or the multilayer ceramic electronic part may be embedded in the board.
In general, the multilayer ceramic electronic part includes a plurality of dielectric layers formed of a ceramic material and internal electrodes inserted between the plurality of dielectric layers. The multilayer ceramic electronic part to be embedded in the board having a high capacitance may be achieved by disposing the multilayer ceramic electronic part in the board.
In order to manufacture the printed circuit board having the multilayer ceramic electronic part embedded therein, after the multilayer ceramic electronic part is inserted into a core board, laser needs to be used to drill via holes in an upper multilayer plate and a lower multilayer plate in order to connect board wirings to external electrodes of the multilayer ceramic electronic part. The laser processing is a factor significantly increasing the manufacturing cost of the printed circuit board.
Meanwhile, since the multilayer ceramic electronic part to be embedded in the board needs to be embedded in a core part in the board, the external electrode thereof does not require a nickel/tin (Ni/Sn) plating layer, unlike a general multilayer ceramic electronic part to be mounted on a surface of the board.
Since the external electrode of the multilayer ceramic electronic part to be embedded in the board is electrically connected to a circuit in the board through a via formed of a copper (Cu) material, a copper (Cu) layer is required on the external electrode instead of a nickel/tin (Ni/Sn) layer.
In general, the external electrode is mainly formed of copper (Cu), but includes glass, such that at the time of laser processing used to form the via in the substrate, an element included in the glass absorbs the laser, whereby a processing depth of the via may not be adjusted.
Due to the reason described above, the external electrode of the multilayer ceramic electronic part includes a copper (Cu) plating layer separately formed thereon.
Meanwhile, the multilayer ceramic electronic part to be embedded in the board is embedded in the printed circuit board used in a memory card, a PC main board, and various radio frequency (RF) modules, such that a size of a manufactured product may be significantly decreased as compared to when a multilayer ceramic electronic part mounted on a board is used.
In addition, since the multilayer ceramic electronic may be disposed significantly close to an input terminal of an active element such as a microprocessor unit (MPU), interconnect inductance due to a length of an electrical wire may be decreased.
A decrease in inductance of the multilayer ceramic electronic part is merely caused by the decrease in the interconnect inductance obtained due to a unique disposition relationship, that is, an embedded scheme, and equivalent series inductance (ESL) properties of the multilayer ceramic electronic part still require improvement.
In general, in the multilayer ceramic electronic part to be embedded in the board, a current path in the multilayer ceramic electronic part needs to be shortened in order to decrease the ESL.
However, the external electrode of the multilayer ceramic electronic part includes the copper (Cu) plating layer separately formed thereon, thereby causing a problem in which a plating solution infiltrates the external electrode, rendering it difficult to shorten the current path in the multilayer ceramic electronic part.